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Plant factory and modern greenhouse

Special Issue:
Plant factory and modern greenhouse

Editor: Eiji Goto and Yasuomi Ibaraki
Target Publication: April 2021


  Thank you for your continuous support to The Horticulture Journal (Hort. J.). With the support of the Japan Society for the Promotion of Science (JSPS) KAKENHI, the Hort. J. will be publishing a special issue series. The journal is seeking original research articles as well as review articles for the special issue ‘Plant factory and modern greenhouse,’ which is planned to be published in April 2021. Dr. Eiji Goto (Chiba University) and Dr. Yasuomi Ibaraki (Yamaguchi University) are serving as guest editors for this special issue. You may submit your manuscript now and up until the deadline, which is 31 September 2020. The selected articles will be published free of charge. Please consider this special issue as a good opportunity to share your excellent work with researchers worldwide.

Areas of specific interest (not limited to):

  • Crop physiology under controlled environments
  • Regulation of physiological and molecular processes by environment control
  • Application of light-emitting diodes and other light sources
  • Monitoring of plant physiological status
  • Advanced cultivation technology

(Any other suggestions are welcome. Please communicate your intention to Hort. J. Editorial Office: hortj@jshs.jp)

 

ORIGINAL ARTICLE
Hongjia Xu, Masahumi Johkan, Satoru Tsukagoshi, Toru Maruo

Advance Online Publication, 2021.|doi: 10.2503/hortj.UTD-207

Abstract

Recently, the number of patients with chronic kidney disease has increased rapidly and kidneys with loss of the K-defecating function have been observed. Thus, providing vegetables with low potassium is an urgent unmet need. In this study, two cultivation methods were used to cultivate lettuce (Lactuca sativa L.) with low K concentrations. One method, dubbed LKEC, was based on electrical conductance management and the K supply was stopped at the end of cultivation. The other method, dubbed LKQM, was based on nutrient quantitative management, and the nutrients required for low-K lettuce were quantitatively supplied. Meanwhile, control lettuce with a normal K concentration, known as CK, were cultivated with electrical conductance management. Compared with CK, both low K treatments reduced the yield by nearly 20% without any visual deficiency symptoms. There was no significant difference between LKEC and LKQM in terms of plant growth. LKQM-treated lettuce contained lower Na and required less fertilizer than LKEC lettuce. Moreover, these plants adapted to K deficiency stress by absorbing more cations to maintain osmotic pressure. N declined with decreasing K. This suggested that the quantitative management method in low-potassium lettuce production reduced the potassium content in the lettuce plants to the same level as the EC management method, and significantly reduced the sodium content compared to EC management.


Abstract

In contrast to fluorescent lamps and high-power sodium lamps, the use of light-emitting diode (LED) lamps enables the control of not only photosynthetic photon flux density (PPFD) at the plant level, but also the relative spectral photon flux density distribution (RSPD) of light because of the variety, even at different times of day, of producible light emitted by LEDs of different types. Effects of the spectral photon flux density on plant growth and morphology have been investigated using several types of LEDs and plant species. However, few studies on lighting methods with time-varying PPFD or RSPD have been published to date. In this paper, we summarize the effects of time-varying PPFD on the net photosynthetic rate (Pn) and those of time-varying RSPD on plant growth and morphology. Detailed modeling studies have been conducted on the reactions of the photosynthetic pathway under time-varying PPFD at a cycle of milliseconds to seconds. The results of these modeling studies and actual measurements of Pn under pulsed light clearly indicate that pulsed light is not advantageous to improve Pn. Although the integrated PPFD of blue and red light was unchanged, the growth of leaf lettuce was promoted by asynchronous irradiation with blue light and red light compared with growth under simultaneous irradiation. We think that blue-light monochromatic irradiation promotes leaf elongation through leaf expansion as a primary factor in the enhancement of plant growth. In addition, changes in leaf photosynthetic capacity caused by blue-light monochromatic irradiation may be involved in plant growth promotion. An increasing number of studies have investigated the effects of time-varying RSPD on plants. However, the mechanisms underlying these effects remain to be elucidated.

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